Micro-electromechanical structure resonator frequency adjustment using radiant energy trimming and laser/focused ion beam assisted deposition

ABSTRACT

The invention relates to a microbeam oscillator. Tuning of the oscillator is carried out by addition or subtraction of material to an oscillator member in order to change the mass of the oscillator member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/738,118, filed on Dec. 15, 2000, and claims priority therefrom under35 U.S.C. § 120. The priority application is currently pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to micro electromechanicalstructure (MEMS) fabrication and, more specifically, the presentinvention relates to the fabrication of a high frequency beam resonator.In particular, the present invention relates to frequency adjustment ofthe high frequency beam resonator.

2. Description of Related Art

As microelectronic technology progresses, the need has arisen forsmaller and higher frequency resonators for both signal filtering andsignal generating purposes among others. The prior state of the art useddiscrete crystals or devices that generate a surface acoustical wave(SAW) for their desired functions. As miniaturization of devicesprogresses, the discrete crystals and SAW generating devices becomerelatively larger and therefore much more difficult to package. Forexample, discrete devices limit the size of the overall system to largerconfigurations and they are more expensive to produce and to install.

Once a resonator is fabricated, process variances may cause a givenresonator to have a frequency that is not within preferred range for agiven application. For such out-of-range resonators, if another usetherefor cannot be found, the resonator must be discarded as a yieldloss.

What is needed is a MEMS resonator that overcomes the problems in theprior art.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and other advantagesof the invention are obtained, a more particular description of theinvention briefly described above will be rendered by reference tospecific embodiments thereof, which are illustrated, in the appendeddrawings. Understanding that these drawings depict only typicalembodiments of the invention that are not necessarily drawn to scale andare not therefore to be considered to be limiting of its scope, theinvention will be described and explained with additional specificityand detail through the use of the accompanying drawings in which:

FIG. 1 is an elevational cross-section view that depicts preliminaryfabrication of a MEMS resonator beam according to the present invention;

FIG. 2 is an elevational cross-section view of the resonator beamstructure depicted in FIG. 1 after further processing;

FIG. 3 illustrates further processing of the structure depicted in FIG.2;

FIG. 4 illustrates further processing of the structure depicted in FIG.3;

FIG. 5 illustrates further processing of the structure depicted in FIG.4;

FIG. 6 illustrates further processing of the structure depicted in FIG.5;

FIG. 7 illustrates further processing of the structure depicted in FIG.6 after formation of a oscillator member layer;

FIG. 8 illustrates a top plan view of the structure depicted in FIG. 7;

FIG. 9 illustrates an elevational cross section view of a cantileveroscillator with patterning for forming spaced apart stacks;

FIG. 10 is an elevational cross-section view the structure depicted inFIG. 9 after the patterning of the protective layer and an ablationlayer;

FIG. 11 is a top plan view of the inventive structure after patterningof the protective layer and an ablation layer;

FIG. 12 is a top plan view of the structure depicted in FIG. 11 afterselective removal of a number of the spaced-apart stacks;

FIG. 13 is an elevational cross-section view of the structure depictedin FIG. 12, taken along the cross-section line 13—13 to illustrate theinventive process;

FIG. 14 is an elevational cross-section view that depicts alternativeprocessing;

FIG. 15 is an elevational cross-section view that depicts alternativeprocessing; and

FIG. 16 is a process flow chart according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description includes terms, such as upper, lower, first,second, etc. that are used for descriptive purposes only and are not tobe construed as limiting. The embodiments of an apparatus or article ofthe present invention described herein can be manufactured, used, orshipped in a number of positions and orientation.

Reference will now be made to the drawings wherein like structures willbe provided with like reference designations. In order to show thestructures of the present invention most clearly, the drawings includedherein are diagrammatic representations of integrated circuitstructures. Thus, the actual appearance of the fabricated structures,for example in a photomicrograph, may appear different while stillincorporating the essential structures of the present invention.Moreover, the drawings show only the structures necessary to understandthe present invention. Additional structures known in the art have notbeen included to maintain the clarity of the drawings.

In a first embodiment, a process of forming a resonator is carried outby removing discrete amounts of material until a preferred resonantfrequency is established. FIG. 1 is an elevational cross-section viewthat depicts preliminary fabrication of a micro electromechanical system(MEMS) resonator beam according to the present invention. A substrate 10is depicted that, in one non-limiting example is a P-type siliconsubstrate that has a high sheet resistance as is known in the art. Uponsubstrate 10 a pad oxide 12 is formed that may have a thickness in arange from about 5,000 Å to about 15,000 Å, and preferably about 10,000Å according to this embodiment. Upon pad oxide 12 a silicon nitridelayer 14 is formed. Silicon nitride layer 14 may be Si_(x)N_(y) such asSi₃N₄ or it may be in other stoichiometric or solid solution ratios. Inthis embodiment, silicon nitride layer 14 may be in a thickness rangefrom about 500 Å to about 1,500 Å, preferably about 1,000 Å. Siliconnitride layer 14 may be formed by deposition such as physical vapordeposition (PVD) or by chemical vapor deposition (CVD). Preferably,silicon nitride layer 14 is formed by low pressure. CVD (LPCVD) underconditions that are known in the art. Upon silicon nitride layer 14 afirst polysilicon layer 16 is formed. First polysilicon layer 16 may beformed by CVD, preferably LPCVD under conditions that are known in theart. First polysilicon layer 16 may be in a thickness range from about2,000 Å to about 4,000 Å, preferably about 3,000 Å according to thisembodiment. Electrical conductivity in first polysilicon layer 16 may beachieved by ion implantation in order to obtain a preferred sheetresistance. Alternatively, doping may be in situ during CVD or LPCVDformation of first polysilicon layer 16.

FIG. 2 illustrates the result of a first mask process to define a bottomelectrode. First polysilicon layer 16 has been segmented into pedestals18 and a bottom electrode 20, also referred to as the drive electrode20. Where the first mask process uses an organic resist, removal of theresist may be carried out by use of an aqueous sulfuric acid (H₂SO₄) andhydrogen peroxide (H₂O₂) solution as is known in the art.

FIG. 3 illustrates the formation of a sacrificial oxide layer 22.Sacrificial oxide layer 22 acts to support what will be an oscillatormember. A deposition process such as the decomposition of tetra ethylortho silicate (TEOS) may be used, or other oxide depositions known inthe art. In this embodiment the thickness of sacrificial oxide layer 22may be in a range from about 50 Å to about 1,000 Å.

FIG. 4 illustrates the effect of patterning with a second mask. Thisprocess exposes part of pedestal 18 that is used as anchorage to whatwill become an oscillator member. In one variation of this embodiment,where sacrificial oxide layer is about 100 Å, an oxide dry etch iscarried out to expose an upper surface 24 of pedestal 18. In anothervariation of this embodiment, where sacrificial oxide layer is about 300Å, an oxide dry etch is carried out to expose an upper surface 24 ofpedestal 18. Where the second mask process uses an organic resist,removal of the resist may be carried out by use of an aqueous sulfuricacid (H₂SO₄) and hydrogen peroxide (H₂O₂) solution as is known in theart.

FIG. 5 illustrates the effect of a process that forms a secondpolysilicon layer 26 that deposits conformably over any topology thatexists upon substrate 10. Second polysilicon layer 26 may be formed byCVD, preferably LPCVD. The thickness of second polysilicon layer will beselected based upon a preferred target frequency of the futureoscillator member. In one variation of this embodiment, secondpolysilicon layer 26 may have a thickness in a range from about 500 Å toabout 1,500 Å, and preferably about 1,000 Å. In another variation ofthis embodiment, second polysilicon layer 26 may have a thickness in arange from about 1,500 Å to about 4,500 Å, and preferably about 3,000 Å.In a manner similar to the ion implantation of first polysilicon layer16, second polysilicon layer may be doped to a preferred sheetresistance that will be selected according to a specific application.Alternatively, doping may in situ during CVD or LPCVD formation ofsecond polysilicon layer 26.

During the process flow, it may be preferred to activate any doping by athermal treatment. In addition to dopant activation, stress relief maybe achieved in the polysilicon structures. Thermal treatment may includean anneal as known in the art for doped and undoped polysiliconstructures, or a faster, rapid thermal anneal (RTA) as known in the artfor polysilicon structures. The specific thermal treatment may beselected according to a specific oscillator quality, both as toresistivity and to stiffness.

FIG. 6 illustrates the effect of processing with a third mask. Theoscillator that is to be formed is patterned from second polysiliconlayer 26. Second polysilicon layer 26 in this non-limiting embodiment,has been formed by a substantial blanket deposition of polysilicon. FIG.6 illustrates the patterning of second polysilicon layer 26 to removeall but the oscillator member portion and the pedestal anchorage portionof second polysilicon layer 26. Accordingly, what may be referred to asan oscillator member 28 or a top electrode 28 is formed according to aprocess that will be further illustrated herein. Etching of secondpolysilicon layer 26 may be carried out under conditions known in theart. One condition is a dry anisotropic polysilicon etch that may betime dependent and/or that stops on subjacent structures such assacrificial layer 22. Where the third mask process uses an organicresist, removal of the resist may be carried out by use of an aqueoussulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂) solution as is knownin the art.

After the removal of the third mask, sacrificial oxide layer 22 may beremoved as depicted in FIG. 7. In one embodiment, sacrificial oxidelayer 22 is wet etched in an aqueous hydrofluoric acid (HF) system.Accordingly, the HF system is selective to the polysilicon structures.Thereafter, the oscillator and substrate are allowed to dry. Drying maybe thermally assisted or it may be vacuum assisted, or both as is knownin the art.

FIG. 8 is a top plan view of an oscillator bridge 30 according to thepresent invention. Top electrode 28 is an oscillator member that spansbetween two pedestals 18. It can be seen that drive electrode 20 mayhave a span beneath top electrode 28 that may vary in size within thedashed area. Additionally, electrical connection 32 to drive electrodecomprises a segment of first polysilicon layer (FIG. 1).

According to the present invention, laser tuning of the inventiveoscillator may be accomplished by forming at least one structure on theoscillator. For example the at least one structure may be a plurality ofspaced-apart stacks. FIG. 9 is an illustration of a cantilever beamoscillator that may be manufactured according to the present invention.

The structures of oscillator pedestal 18 and top electrode 28 maycomprise an electrically conductive material. One example of anelectrically conductive material is polysilicon according to theembodiment set forth herein. The polysilicon is selected from undopedpolysilicon and doped polysilicon, either p-doped or n-doped. Anotherexample of an electrically conductive material is a metal such as metalsthat are typically used in the fabrication of metallization layers. Themetal may be selected from aluminum, copper, silver, gold, and the like.The metal may also be selected from titanium, niobium, zirconium,hafnium, and the like. The metal may also be selected from tungsten,cobalt, nickel, scandium and others known in the art. Another example ofan electrically conductive material is refractory metal nitridesselected from titanium nitride, tantalum nitride, tungsten nitride,aluminum nitride, combinations thereof, and the like.

According to one embodiment, after the formation of top electrode 28,and preferably before the removal of sacrificial oxide layer 22, theentire structure may be treated to make the resonator structure anintegral unit. Where pedestal 18 and top electrode 28 are polysilicon,treatment may be a rapid thermal process (RTP) such a heating in aninert environment over a temperature increase range from about 100° C.to about 2,000° C. and for a process time from about 10 seconds to about5 minutes. In order to provide a microfine-grained, substantiallyhomogenous polysilicon resonator structure that will resistdisintegration during field use, it is preferable to use a polysiliconcomposition that has a grain size in a range from about 0.1 micron toabout 10 micron and an aspect ratio from about 1:1 to about 4:1,preferably from about 1.1:1 to about 2:1. Preferably, the polysilicon isdoped by implanting doping elements at the borders between individualhomogenous phases of the polysilicon.

Where top electrode 28 and pedestal 18 are made of a metal, fabricationmay be preferably carried out by sputtering. An RTP may also be carriedout to anneal the composite structure. In any event, the resonantfrequency of a beam, bridge or a plate/membrane is a function of bothresonator stiffness and resonator mass. Accordingly, a preferredresonant frequency, a preferred oscillation frequency or the like may beachieved in part by selecting a material according to its knownstiffness.

After the formation of top electrode 28, a protective layer 30 and anablative layer 32 are formed over oscillator member 28 as depicted inFIG. 9. A fourth mask 34 is patterned over ablative layer 32 inpreparation for the formation of spaced-apart stacks that may beselectively removed for oscillator tuning. Protective layer 30 may actas a diffusion barrier that may be made from materials such as titanium(Ti), chromium (Cr), silicon (Si), thorium (Th), cerium (Ce), alloysthereof, combination thereof, and the like. Metal oxide compounds may bealso used such as titania, chromia, silica, thoria, and ceria. Metalnitride compounds may also be used such as Ti_(x)N_(y), Cr_(x)N_(y),Si_(x)N_(y), Th_(x)N_(y), Ce_(x)N_(y), and the like. Metal silicidecompounds may also be used such as Ti_(x)Si_(y), Cr_(x)Si_(y),Th_(x)Si_(y), Ce_(x)Si_(y), and the like. In any event the metal oxide,the metal nitride, and the metal silicide compounds may be provided inboth stoichiometric and solid solution ratios.

FIG. 10 illustrates cantilever beam oscillator 100 after furtherprocessing. Other oscillator structures may be used such as microbridgeresonators and the like as illustrated in FIG. 8 or the like, membraneresonators and the like, and other resonators. In the present inventiona cantilever beam oscillator 100 is used to illustrate the inventivemethod. FIG. 10 illustrates cantilever beam oscillator 100 after furtherprocessing in which sacrificial oxide layer 22 has been removed. Theremoval process may be done by isotropic etching, preferably by wetetching. Etch selectivity in the preferable isotropic wet etch isconfigured to make the etch recipe less selective to sacrificial oxidelayer 22, than to any and all of substrate 10, drive electrode 20,oscillator pedestal 18, and top electrode 28. The etch recipeselectivity is above about 20:1, preferably below about 100:1, morepreferably below about 1000:1, and most preferably below about 5000:1.After the removal process, it is observed that top electrode 28 isdisposed spaced apart from drive electrode 20. Optionally, the removalof sacrificial oxide layer 22 may precede formation of protective layer30 and ablative layer 32, or following removal of ablative structure 40.

A plurality of spaced-apart stacks 36 include a protective pad 38 thatis formed from protective layer 30, and ablative structure 40 that isformed from ablative layer 32. The spaced-apart stacks 36 are patternedupon a first surface 42 of oscillator 100. As illustrated in FIG. 10,protective pad 38 was simultaneously patterned out of protective layer30, while ablative structure 40 was patterned out of ablative layer 32.Ablative structure 40 is preferably made from a material that willvaporize at the intensities of a focused ion beam (FIB) or a laser.Protective pad 38 acts to resist damage to upper surface 42 ofoscillator member 28 during removal the ablative structure 40 ofselected spaced-apart stacks 36. The material of protective pad 38 maybe selected from a refractory metal, a refractory metal silicide, arefractory metal nitride, and combinations thereof. For example arefractory metal silicide may be Ti_(x)Si_(y), wherein x and y areconfigure for both stoichiometric and other solid solution combinations.Alternatively, protective pad 38 may be selected from a silicon-basedcomposition such as polysilicon and the like for both doped and undopedpolysilicon. Other silicon-based compositions may include silicon oxidesuch as Si_(x)O_(y) such as stoichiometric silica and the like in bothstoichiometric and other solid solution combinations. Othersilicon-based compositions may include silicon nitride such asSi_(x)N_(y) for example Si₃N₄ and the like in both stoichiometric andother solid solution combinations.

Optionally, protective pad 38 may be patterned through a negative maskby patterning the mask with a plurality of recesses, and by successivelylining the recesses with protective pad 38, followed by second fillingthe recesses with ablative material 40. Thereafter, a planarization suchas chemical mechanical planarization (CMP) or the like, or a plasmaetchback or the like may be carried out. In order to achieve a structuresimilar to that depicted in FIG. 10, the formation of protective pad 38is preferably carried out by collimated physical vapor deposition (PVD).Alternatively, protective layer 30 may be unpatterned such that the massthereof is figured into the ultimate frequency of oscillator 100.

Removal of selected spaced-apart stacks 36 is carried out by determininga first resonant frequency of top electrode 28 and removing at least oneof the spaced-apart stacks 36 with a radiant energy source. The radiantenergy source is selected from a laser and the like, an ion beam and thelike, and combinations thereof. Preferably, the radiant energy source isa laser that may be used for laser ablation. By removal of thespaced-apart stack 36, it is meant that ablative structure 40 is removedaccording to the present invention, and that protective pad 38 may ormay not be removed in whole or in part.

In one embodiment of the present invention, the removal of selectedspaced-apart stacks 36, or one of them, is carried out in a passive orstatic implementation. In this embodiment, a first resonant frequency isdetermined, at least one spaced-apart stack 36 is removed, and secondresonant frequency is determined by vibrating the oscillator 100 afterremoval of at least one spaced-apart stack 36. In another embodiment ofthe present invention, the removal of selected spaced-apart stacks 36,or one of them, is carried out in an active or dynamic implementation.In this embodiment, a second resonant frequency is determined bymonitoring any change in resonant frequency while simultaneouslyremoving selected spaced-apart stacks 36, one of them, or a portionthereof where radiant energy controls may be sufficiently sensitive.

FIG. 11 is a top plan view of the oscillator 100 depicted in FIG. 10 toillustrate a pattern formed of the ablative layer 32 and of spaced-apartstacks 36. During removal of selected spaced-apart stacks 36, or one ofthem, an empirical removal pattern is established upon oscillator 100.FIG. 12 is an illustration of a removal pattern 44 that may arise fromcombination of empirical and/or academic knowledge of a preferredconfiguration of spaced-apart stacks 36 that are selected for removalbased upon a delta in the first resonant frequency and a preferredsecond resonant frequency. Empirical and/or academic knowledge may thenbe applied to a second resonator in the same process batch.Alternatively, the second resonator may be located in a region in asecond wafer or the like that is likely to have similar process results.Alternatively, a second resonator may be located on a second wafer thatmay have had similar process conditions as the first resonator.Additionally, a combination of a similar process wafer and a similarregion of a wafer may be combined to select the second resonator.Additionally, a progressive stepping across a given wafer may be carriedout under conditions that allow for finite difference tracking ofchanges in the first resonant frequency, and stack removal may beadjusted in response previous empirical data obtained for the givenwafer or for a previous wafer that may have been processed under similarconditions.

The final frequency of oscillator 100 is based upon the mass ofremaining spaced-apart stacks 36, and a respective position of each atleast one spaced-apart stack 36 along the top electrode 28 that is notremoved, under conditions to approach a second resonant frequency. FIG.13 is an elevational cross-section view taken along the line 13—13 fromFIG. 12. FIG. 13 depicts the structure of oscillator 100 after removalof the ablative structure 40 of at least one spaced-apart stack 36.Preferably, removal of a spaced apart stack 36 is carried out bydirecting a radiant energy source toward a selected spaced-apart stack36. Because the ablative layer is now configured as a plurality ofdiscrete ablative structures 40 that make up spaced-apart stacks 36, aradiant energy beam that is directed toward a selected spaced-apartstack 36 has sufficient margin for a radiant beam overlap error that islimited to the area immediately surrounding a given spaced-apart stack36, without impinging upon an adjacent spaced-apart stack 36. In thisway, a substantially discrete amount of material, that is a singleablative structure 40, is removable from upper surface 42 such thatsubstantially discrete tuning of oscillator 100 may be carried out. Apreferred source of radiant energy is a laser. In the present invention,the duration and intensity of the radiant energy source is lesseffective to remove a discrete amount of material, compared to theremoval of a discrete spaced-apart stack 36 or the ablative structure 40portion of a spaced-apart stack 36.

In one embodiment, oscillator 100 is a beam such as a cantilever beam.For some applications such as a hand-held telecommunications use by wayof non-limiting example, the mass of oscillator 100 is in the range fromabout 0.1×10⁻⁷ gram to about 10×10⁻⁷ gram. The process may be carriedout in this embodiment wherein each of the spaced-apart stacks 36 has amass in a range from about 0.02% the mass of the oscillator 100 to about2% the mass of oscillator 100.

In one embodiment of the present invention, sacrificial oxide layer 22is removed before the selective removal of at least one spaced-apartstack 36. In a first alternative of this embodiment, selective removalof at least one spaced-apart stack 36 is carried out in the passive orstatic mode wherein oscillator 100 is not being tested in motion. In asecond alternative of this embodiment, selective removal of at least onespaced-apart stack 36 is carried out in the active or dynamic modewherein oscillator 100 is being tested in motion. In either embodiment,intermittent testing of oscillator 100 may be carried out to achieve apreferred resonant frequency. In another embodiment, sacrificial oxidelayer 22 is removed after the selective removal of at least onespaced-apart stack 36.

FIG. 14 illustrates another embodiment of the present invention. In thisembodiment, an oscillator 200 includes a sacrificial oxide layer 22 tosupport the oscillator member 28. This embodiment represents a passiveor static tuning of oscillator 200. Bulk material 46 is added tooscillator 200 by the use of a radiant energy source 48 such as a laseror a focused ion beam (FIB) in the presence of a deposition vapor. Bulkmaterial 46 acts to deposit upon upper surface 42 at the conjunction ofthe deposition vapor, the radiant energy source 48, and upper surface42. In this manner, bulk material 46 is added by directing radiantenergy source 48 over a preferred amount of upper surface 42. Bulkmaterial 46 may be a compound such at SiO₂ formed from the thermaldecomposition of tetraethyl ortho silicate (TEOS). It may also be ametal such as tungsten (W), chromium (Cr), cobalt (Co), nickel (Ni),platinum (Pt), alloys thereof, combinations thereof, and the like.Although not depicted, it is understood that where necessary to protectoscillator member 28 during the formation of bulk material 46, aprotective layer such as protective layer 30 may be formed upon uppersurface 42.

In another embodiment, the active or dynamic tuning of oscillator 200 iscarried out as illustrated in FIG. 15. Sacrificial oxide layer 22 hasbeen removed, oscillator 200 is in motion 50, and radiant energy source48 is building a bulk material 46 while the frequency of oscillator 200is being monitored. As the vapor impinges oscillator 200, the vaporforms condensate and/or a precipitate that is deposited by suchmechanisms as decomposition of the vapor into an at least in partnon-volatile portion. The conditions that are sufficient to cause theimpinging vapor to deposit to form bulk material 46 may be practicedaccording to known methods of laser or FIB deposition techniques. Suchconditions may also be selected from either the preferred CVD processesor from PVD processes.

In any event, an empirical process may include determining a firstresonant frequency of oscillator 200, patterning at least one structuresuch as ablative structure 40 (subtractive patterning) or bulk material46 (additive patterning) on oscillator upper surface 42, and thendetermining a second resonant frequency of oscillator 200.Alternatively, the inventive method may include continuously monitoringthe resonant frequency of oscillator 200 as it changes from the firstfrequency to the second frequency by continuously vibrating theoscillator 200 while patterning.

The inventive oscillator is typically a component that may be placed inan electronic device such as a handheld and/or wireless device. Suchhandheld and/or wireless devices may include a personal data assistant(PDA), a cellular telephone, a notebook computer, and the like. Theinventive oscillator is also typically placed in an electronic devicesuch as a storage device including a magnetic storage device and thelike where the oscillator may be a read/write structure.

FIG. 16 illustrates the inventive process 300. First, an oscillator isprovided 310 that includes an oscillator member. A first resonantfrequency of the oscillator member is determined 320. Next, at least onestructure is patterned 330 on the oscillator member. This patterning iseither subtractive, additive or both. Next, a second resonant frequencyof the oscillator member is determined 340.

In one embodiment of the present invention, because of both passive andactive patterning techniques, either or both of which can be additive orsubtractive, an oscillator may be tuned to meet a preferred application.It will become clear that both subtractive and additive techniques maybe combined such that the subtractive technique acts as a discrete stagetuning where a slight overshoot may occur, and then the additivetechnique acts as a continuous tuning to bring the preferred resonantfrequency closer to the preferred number. Control of the additivetechnique may be dominated by the presence and physical state of thedeposition vapor where adjustment of a laser or an FIB may lack theneeded sensitivity to achieve a preferred resonant frequency. In otherwords, the subtractive technique approaches a digital adjustment to apreferred resonant frequency for an oscillator, and the additivetechnique approaches an analog adjustment to the preferred resonantfrequency.

It will be readily understood to those skilled in the art that variousother changes in the details, material, and arrangements of the partsand method stages which have been described and illustrated in order toexplain the nature of this invention may be made without departing fromthe principles and scope of the invention as expressed in the subjoinedclaims.

1. A micro resonator comprising: an oscillator member comprising avibrating portion supported by a pedestal; and an ablative structuredisposed on the vibrating portion, the ablative structure comprising apattern of spaced-apart stacks, each spaced-apart stack being separatedfrom the oscillator member by a protective pad.
 2. The micro resonatoraccording to claim 1 wherein the protective pad is made from aluminum,an aluminum alloy, silver, a silver alloy, indium, or an indium alloy.3. The micro resonator according to claim 1 wherein the protective padis made from a refractory metal, a refractory metal oxide, a refractorymetal silicide, a refractory metal nitride, or combinations thereof. 4.The micro resonator according to claim 1 wherein the oscillator memberis made of a material selected from polysilicon, a metal, a metalnitride, a metal oxide, a metal silicide, or combinations thereof.
 5. Amicroresonator system comprising: a microresonator having an input andan output and comprising: an oscillator member comprising a vibratingportion suspended above a substrate by a pedestal, a drive electrodepositioned between the vibrating portion and the substrate, an ablativestructure disposed on the vibrating portion, the ablative structurecomprising a pattern of spaced-apart stacks, each spaced-apart stackbeing separated from the oscillator member by a protective pad; an inputcircuit connected to the input; and an output circuit connected to theoutput.
 6. The micro resonator according to claim 5 wherein theprotective pad is made from aluminum, an aluminum alloy, silver, asilver alloy, indium, or an indium alloy.
 7. The micro resonatoraccording to claim 5 wherein the protective pad is made from arefractory metal, a refractory metal oxide, a refractory metal silicide,a refractory metal nitride, or combinations thereof.
 8. The microresonator according to claim 5 wherein the oscillator member is made ofa material selected from polysilicon, a metal, a metal nitride, a metaloxide, a metal suicide, or combinations thereof.